This paper investigates the problem of dynamic multiuser subchannel allocation in the downlink OFDM systems. In traditional TDMA or FDMA systems, resource allocation for each user is non-adaptively fixed. Since the subchannel allocations among the users are not optimized, a group of users is likely to suffer from poor channel gains resulting from large path loss and random fading. To resolve this problem a low-complexity adaptive subchannel allocation algorithm is proposed in this paper. By... Topics: OFDM, Sub-Channel, Multiuser, Variable Data Rate.